Installation for heating drying drums of drying machines



Aug. 25, 1964 H. GERSTER 3,146,078

INSTALLATION FOR HEATING DRYING DRUMS OF DRYING MACHINES Filed Feb. 15.1961 FIGI FIGZ

INVENTOR.

HElNRlCH GERSTER l0 l2 BY L A TTORNEYS United States Patent 3,146,078INTALLATEON FOR HEATING DRYING DRUMS 0F DRYING MACHINES HeinrichGerster, Industriestrasse 1, Bruchsal-Karlsdorf, Baden, Germany FiledFeb. 15, 1961, Ser. No. 89,459 Claims priority, application Germany Feb.20, 1950 1 Claim. (Cl. 34-123) The present invention relates to aninstallation for heating the drying drum of a drying apparatus fordrying photographic prints which is rotatably supported on a horizontalshaft and against which abuts, over a section of the periphery thereof,a drying cloth in the form of an endless band which is adapted to movein the same direction as the drum.

The drying drums of the known prior art drying apparatus forphotographic prints are heated, for the most part, by the supply of warmor heated air to the drum inside. By reason of the relatively slightheat capacity of the air, the sections of the drum consisting ofrelatively thin steel sheet metal members which serve for purposes ofdrying are cooled off very rapidly and are not brought back sufficientlyrapidly to the temperature required for drying. The warm air serving forpurposes of heating must not exceed a predetermined temperature as theuse of excessively high temperatures entails the danger of unevenheating with the consequence of uneven drying and local overheating ofthe drum. Consequently, the heating of the drying drum with warm airleads to frequent occurrences of defective operation as regardsphotographic prints produced thereby and therewith involves additionalexpenses.

It has already been attempted to achieve a better heat conduction andheat distribution by the application, along the inside of the drum, of agood heat conducting material, for example, by plating the same withcopper. This measure, however, does not entail the expected advantagesand, under certain circumstances, causes a contrary effect, for example,in case of a plating which is not completely satisfactory. This is so asin those places in which the applied material does not abut thereagainstclosely to form a good intimate contact with the base material,heat-insulating air gaps result therefrom by means of which the heatexchange is additionally deteriorated.

Drum heating systems are also known in the art in which the annularspace of a double-walled drum is filled with liquid which iselectrically heated. The realization of such a construction, however, isvery complicated and involves high manufacturing costs. Additionally,the circulation of the fluid can be achieved only with difficulties andleads often times to failures and breakdowns.

The present invention is concerned with the aim to produce anarrangement in which the sections of the drying drum which are intendedfor purposes of drying the photographs are heated sufliciently andevenly during rotation of the drying drum without large expenditures.This aim and problems connected therewith are solved according to thepresent invention by constructing the drum in a fluid-tight manner andby arranging along the inside of the drum casing pockets, constituted bystrips extending essentially parallelly to the drum axis, for theaccommodation or reception therein of a liquid heatcarrier or heatingmedium, such as water, which is maintained at a predeterminedtemperature and is disposed in a sump located within the lower part ofthe drum.

By a thorough covering of the inside of the cylinder casing with suchpockets, there is achieved an even heating of the section of thecylinder casing serving for purposes of drying. The pockets discharge,during rotation thereof, the heat-carrier or heating-medium, preferablyice water, as soon as they reach or pass beyond the top point or apex ofthe path of the drum. The section of the cylinder casing having therespectively discharged pockets cools off slightly which is desirableduring operation of the drying drum. Water, by reason of its good heattransmitting and high heat capacity characteristics is recommendable inparticular as heat carrier. In order to enable heating of the heatcarrier, an electric heating member is arranged within the lower sectionof the drum within the area of the sump occupied by the heat carrier.Appro priately, the drum shaft is thereby constructed as stationaryhollow shaft and is provided with externally arranged roller bearingsfor the drum. The heating body is then secured at the hollow shaft ofthe drum and the input and output lines are extended through the hollowshaft.

It may be of advantage for certain operating conditions not to maintainthe rising section of the drum casing at an essentially constanttemperature but, instead, to permit the temperature to drop during therise thereof. For that purpose, the pockets may be provided at the lowernormally closed edge thereof adjoining the drum casing with apertures ofslight size, the size being so dimensioned that the pockets aredischarged only partially during the rotation of the drum through aboutAs a result thereof, the quantity of heat-carrier or heating-mediumtaken along in each pocket decreases con stantly during the rise of thedrum, and the heat given ofl? to the surroundings of the pocket therebydecreases with an increasing rise of the corresponding area of the drumcasing.

Accordingly, it is an object of the present invention to provide aheating system for the drying drum of a drying apparatus, especially fordrying photographic prints, which effectively eliminates theshortcomings and inadequacies of the prior art constructions in a simplemanner.

Another object of the present invention resides in the provisions of asimple heating means utilizing a heat carrier of high heat capacity andheat transmission characteristics, such as water, which permits, in asimple manner, the realization of predetermined heating over the sectionof the drum normally used for purposes of drying the photographicprints.

A still further object of the present invention resides in the provisionof heating means utilizing a high thermal capacity liquid which permitsthe establishment of a predetermined heat gradient over the section ofthe drying drum used for drying purposes.

These and other objects, features, and advantages of the presentinvention will become more obvious from the following description, whentaken in connection with the accompanying drawing which shows, forpurposes of illustration only, one embodiment in accordance with thepresent invention, and wherein FIGURE 1 is a schematic cross sectionalview of a drying drum provided with a heating installation according tothe present invention, and

FIGURE 2 is a schematic longitudinal cross sectional view through thedrying drum of FIGURE 1.

Referring now to the drawing wherein like reference numerals are usedthroughout the two views to designate corresponding parts, referencenumeral 1 designates therein a frame of any suitable construction. Ahollow shaft 3, which is secured at the frame 1 in any suitable manner,rotatably supports thereon, with the aid of roller bearings 8, a dryingdrum formed of two end walls 5 and the cylinder casing 6 having a highlypolished and surface-protected outer surface. A drying cloth 10 abutsagainst the cylinder casing 6 over a relatively large section of thecircumference thereof, which drying cloth is constructed as an endlessband and is guided or returned back upon itself, with the aid of rollers12 supported in the frame 1, over the section thereof that is in contactor abuts against the cylinder casing 6. The drum 5, 6 is supported in afreely rotatable manner by means of bearings 8, while the drying cloth10 is adapted to be driven with the aid of any suitable motor (notillustrated) thereby imparting a rotary movement to the drying drum bythe operative engagement therewith of a portion of the endless dryingcloth 10.

The two rim portions of the cylinder casing 6 are inserted into the gapopen toward the inside of a sealing ring of essentially U-shaped crosssection which is disposed in an annular trough or stiffening corrugationalong the outer periphery of the end walls 5. The mutually opposite endwalls 5 are kept together in the assembled, fluid-tight condition bytensioning or tie rods of any suitable construction (not illustrated).

Relatively fiat pockets are arranged along the inner walls of thecylinder casing 6 which are each constituted by a sheet metal strip, astrip of synthetic material, of the like. The strips forming the pockets15 are disposed essentially parallelly to the drum axis and extend fromone to the other end wall 5 of the drum. The pockets 15 are spaced alongone entire longitudinal edge thereof, over the full width thereof, by apredetermined distance from the inner drum wall, whereas the otherlongitudinal edge of each pocket abuts directly against the inner drumwall. The strips forming the pockets 15 are secured, in any known andappropriate manner, along the rim portions thereof at the cylindercasing 6, the manner of securing depending on the material used, forexample, by bonding, cementing, gluing or the like.

Apertures 17 may be provided in the longitudinal edge of each pocketdisposed opposite the open side of each pocket, which apertures 17 areso dimensioned that during one half of one drum rotation, not the entireliquid contained in the respective pocket 15 but only a predeterminedportion thereof is discharged therefrom.

A heating member 19 of any suitable type is secured on the stationaryhollow shaft 3, which heating member 19 is disposed within the watersump slightly above the lowest point of the drum. The supply of currentto the electric heating member 19 is extended through the hollow shaft 3and is realized by any suitable means, such as an electric wire, cableor the like.

The drum 5, 6 is filled up to a predetermined height with a heatcarrier, preferably water. The heat carrier is maintained at apredetermined temperature by the heating body 19 of any suitableconstruction which is adapted to be electrically controlled by athermostat 20 effectively extending with the sensing element into theheat carrier or heating medium.

Upon rotation of the drum 5, 6 in the clockwise direction as viewed inFIGURE 1, the pockets 15 disposed along the inside of the cylindercasing 6 are submerged in the water sump, are filled with water as theheat carrier, and then take along the water over the path up to the apexor top point of the drum. A predetermined quantity of water isdischarged through the respective apertures 17 of each pocket 15 duringthe drum rotation and flows back along the drum wall into the sump.Within the area of the apex or top point of the drum rotation, thepockets 15 discharge the remaining amount of water through the open sidethereof and the water thereby falls back into the sump. By reason oftaking along the water as heat carrier, the rising cylinder casingsection is maintained approximately at the same temperature and is notcooled off significantly from the outside since the water gives off heatcontinuously.

Operation The operation of the drying drum according to the presentinvention is as follows:

During operation of the drying drum, the watered photographic prints areplaced on the portion of the drying cloth 10 entering the drum with theemulsion of the film facing upwardly and are thereupon taken alongbetween the driven drying cloth 10 and the drum 5, 6, itself taken alongby the movement of the drying cloth 10. As a result of the heat of thedrying drum, the prints are dried and leave the conveyer path at theupper reversing place of the drying cloth 10 where they either fall offby themselves or may be taken off by means of a suitable deflectormember or the like.

While I have shown and described one embodiment in accordance with thepresent invention, it is understood that the same is not limited theretobut is susceptible of many changes and modifications within the spiritand scope of the present invention, and I, therefore, do not wish to belimited to the details shown and described herein but intend to coverall such changes and modifications as are encompassed by the scope ofthe appended claim.

I claim:

An arrangement for heating the drying drum of a drying apparatus,especially for drying photographic prints, comprising a relativelystationary, approximately horizontal hollow shaft, drum means having adrum casing, means including bearing means on said shaft for rotatablysupporting said drum means about said hollow shaft, drying cloth meansadapted to be moved in the same direction as said drum means andabutting against a section of the circumference of said drum means, saiddrying cloth means being in the form of an endless band, said drum meansbeing of liquid-tight construction, and pocket means arranged along theinner side of the casing of said drum means for receiving therein aliquid heatcarrier maintained at a predetermined temperature, saidpocket means being formed by strips extending essentially parallelly tothe drum axis and being filled from a sump of liquid heat-carrierlocated in the lower portion of said drum means upon rotation of saiddrum means, electric heating means disposed within the lower area ofsaid drum means in which is located said sump for heating said liquidmedium, said electric heating means including wire means adapted to beconnected to the electric circuit and extending through said hollowshaft, and means for supporting said electric heating means on saidhollow shaft.

References Cited in the file of this patent UNITED STATES PATENTS i1,258,055 St. Clair et al Mar. 5, 1918 1,483,343 Gladin Feb. 12, 19242,365,271 Hornbostel Dec. 19, 1944 2,365,678 Butler Dec. 26, 19442,413,567 Hornbostel Dec. 31, 1946 2,964,297 Davis et al. Dec. 13, 19603,002,290 Abdoo Oct. 3, 1961 3,071,870 Schnoring et al. Ian. 8, 1963

